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Model ring oscillator VCO

**Library:**Mixed-Signal Blockset / PLL / Building Blocks

The Ring Oscillator VCO block models the output signal, frequency control, period jitter, and flicker noise of a VCO (voltage controlled oscillator) such as a bias controlled ring oscillator circuit. This block generates the phase noise using a mathematical description of the phase noise of ring oscillators. This allows faster computation of simulation results during both startup and the subsequent simulations. You can also control the phase noise profile by selecting the Gaussian noise level, corner frequency, and flicker exponent. The phase noise spectrum is limited to the spectra that can be produced by the physical model of a ring oscillator.

You can choose the coefficients for the mathematical description of the phase noise. You can provide a specific phase noise spectral density from a data sheet and compare that to the phase noise spectral density that the mathematical coefficients produce. You can then adjust the coefficients to fit the specified phase noise in a way that makes the most sense physically.

**Note**

If the flicker noise corner frequency is set to zero, the Ring Oscillator VCO block can also be used to model a tank-tuned VCO.

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